Two-stage hydrotreating of hydrocarbons

Abstract

A method of processing a hydrocarbon feedstock may comprise hydrotreating the hydrocarbon feedstock in a low-severity hydrotreater to produce a first effluent and hydrotreating the first effluent, or a portion thereof, in a high-severity hydrotreater to produce a low contaminant product. The low-severity hydrotreater may operate at a catalyst volume of less than 60% of a catalyst volume of the high-severity hydrotreater. The low-severity hydrotreater may operate at a hydrogen partial pressure of at least 5 bar lower than the hydrogen partial pressure in the high-severity hydrotreater. The low-severity hydrotreater may operate at a weighted average bed temperature (WABT) of at least 5° C. less than the WABT of the high-severity hydrotreater.

What is claimed is: 
     
       1. A method of processing a hydrocarbon fraction, the method comprising:
 hydrotreating the hydrocarbon feedstock in a low-severity hydrotreater to produce a first effluent, and 
 hydrotreating the first effluent, or a portion thereof, in a high-severity hydrotreater to produce a low contaminant product; wherein
 the low-severity hydrotreater operates at a catalyst volume of less than 60% of a catalyst volume of the high-severity hydrotreater; 
 the low-severity hydrotreater operates at a hydrogen partial pressure of at least 5 bar lower than the hydrogen partial pressure in the high-severity hydrotreater; and 
 the low-severity hydrotreater operates at a weighted average bed temperature (“WABT”) of at least 5° C. less than the WABT of the high-severity hydrotreater. 
 
 
     
     
       2. The method of  claim 1 , wherein the low-severity hydrotreater operates at a catalyst volume of less than 20% of a catalyst volume of the high-severity hydrotreater. 
     
     
       3. The method of  claim 1 , wherein the high-severity hydrotreater operates at a LHSV of from 0.5 h −1  to 2 h −1 . 
     
     
       4. The method of  claim 1 , wherein the low-severity hydrotreater operates at a LHSV of from 5 h −1  to 15 h −1 . 
     
     
       5. The method of  claim 1 , wherein the low-severity hydrotreater operates at a hydrogen partial pressure of at least 25 bar lower than the high-severity hydrotreater. 
     
     
       6. The method of  claim 1 , wherein the low-severity hydrotreater operates at a hydrogen partial pressure of less than 40% of the hydrogen partial pressure of the high-severity hydrotreater. 
     
     
       7. The method of  claim 1 , wherein the low-severity hydrotreater operates at a hydrogen partial pressure from 5 to 30 bar. 
     
     
       8. The method of  claim 1 , wherein the high-severity hydrotreater operates at a hydrogen partial pressure of from 40 to 65 bar. 
     
     
       9. The method of  claim 1 , wherein the low-severity hydrotreater operates at a WABT of at least 15° C. less than the WABT of the high-severity hydrotreater. 
     
     
       10. The method of  claim 1 , wherein the low-severity hydrotreater operates at a WABT of from 300 to 350° C. 
     
     
       11. The method of  claim 1 , wherein the high-severity hydrotreater operates at a WABT of from 350 to 450° C. 
     
     
       12. The method of  claim 1 , wherein the hydrocarbon feedstock has greater than 1000 ppm of sulfur. 
     
     
       13. The method of  claim 1 , wherein the first effluent has less than 70% of the sulfur content of the hydrocarbon fraction. 
     
     
       14. The method of  claim 1 , wherein the low contaminant product has less than 10 ppm of sulfur. 
     
     
       15. The method of  claim 1 , wherein
 hydrotreating the hydrocarbon feedstock comprises exposing the hydrocarbon feedstock to a low-severity hydrotreating catalyst in the presence of hydrogen gas; 
 hydrotreating the first effluent comprises exposing the first effluent to a high-severity hydrotreating catalyst in the presence of hydrogen gas; and 
 the low-severity hydrotreating catalyst and the high-severity hydrotreating catalyst each comprise less than 5 wt. % of precious metals. 
 
     
     
       16. The method of  claim 1 , wherein
 hydrotreating the hydrocarbon feedstock comprises exposing the hydrocarbon feedstock to a low-severity hydrotreating catalyst in the presence of hydrogen gas; 
 hydrotreating the first effluent comprises exposing the first effluent to a high-severity hydrotreating catalyst in the presence of hydrogen gas; and 
 the low-severity hydrotreating catalyst and the high-severity hydrotreating catalyst each comprise a supported transition metal. 
 
     
     
       17. The method of  claim 1 , wherein hydrogen sulfide and/or ammonia gasses are removed from the first effluent between the low-severity hydrotreater and the high-severity hydrotreater. 
     
     
       18. The method of  claim 1 , wherein at least 90 wt. % of the first effluent from the low-severity hydrotreater is fed to the high-severity hydrotreater and at least 90 wt. % of the feed to the high-severity hydrotreater comprises the first effluent. 
     
     
       19. The method of  claim 1 , wherein the hydrocarbon feedstock comprises greater than 500 ppm of sulfur. 
     
     
       20. The method of  claim 1 , wherein the hydrocarbon feedstock comprises a whole crude or a fraction of a whole crude.